In recent years, as an example of a particle-movement type display apparatus that effects display by moving particles, an electrophoretic display apparatus designed to effect display by moving electrophoretic particles under application of a voltage has been actively studied.
Such an electrophoretic display apparatus includes a pair of substrates disposed with a spacing therebetween, an insulating liquid and electrophoretic particles which are disposed in the spacing, and a pair of electrodes disposed close to the insulating liquid. The electrophoretic display apparatus has, compared with a liquid crystal display apparatus (device), various advantages, such as a high display contrast, a wide viewing angle, a display memory characteristic, an elimination of the need for a backlight and a polarizing plate, etc.
However, the electrophoretic display apparatus effects display by reflecting external incident light, so that an amount of external light incident thereon is decreased when an illuminance of the external light is low, e.g., the electrophoretic display apparatus is used indoors or during the night. As a result, the display state is very dark, so that the electrophoretic display apparatus has a disadvantage of lowering its viewability. For this reason, the electrophoretic display apparatus is required to increase a reflectance so as to efficiently reflect the incident external light.
In a reflection type liquid crystal display apparatus which effects display by reflecting external light incident thereon similarly as in the electrophoretic display apparatus in order to retain an enlarged viewing angle and enhance a reflectance, Japanese Laid-Open Patent Application No. Hei 11-109392 has proposed a structure in which a reflection electrode at each pixel is provided with a portion with a directivity with respect to the incident external light and a portion exhibiting a mirror surface characteristic.
In such a structure, light fluxes, of the incident external light, which enter the portion of the reflectance electrode having the mirror surface characteristic are regularly reflected by the reflection electrode, so that all the light fluxes are moved outside a liquid crystal cell. As a result, it is possible to increase a reflectance and a contrast. Light fluxes which enter the portion of the reflection electrode having the directivity are scattered by the reflection electrodes and moved in the scattering direction to increase an outgoing angle, thus keeping an enlarged viewing angle.
Similarly, when such a structure for reflecting the light is employed in the electrophoretic display apparatus, it is possible to increase the reflectance, FIGS. 13(A) and 13(B) are schematic views showing a structure of one pixel in the case where a scattering layer of such a conventional reflection type liquid crystal display apparatus is employed in an electrophoretic display apparatus, wherein FIG. 13(A) is a plan view of the pixel and FIG. 13(B) is a sectional view of the pixel along X-Y line shown in FIG. 13(A).
Referring to these figures, the electrophoretic display apparatus includes a first substrate 1A and a second substrate 2A which are disposed opposite to each other with a spacing there a closed space, in which an insulating liquid 3 and a plurality of electrophoretic particles 4 are filled, is disposed. In the closed space, a first substrate 25 and a second electrode 26 are disposed close to the insulating liquid 3 and between which a voltage is applied to move the electrophoretic particles 4 toward the first electrode 25 or the second electrode 26, thus effecting display. Between the first electrode 25 and the insulating liquid 3, an isotropic scattering layer 12 is disposed, and a plurality of partition walls 7A are disposed to partition the spacing between the first and second substrates 1A and 2A into a plurality of closed spaces each corresponding to one pixel. Accordingly, each of the partition walls 7A is disposed at a pixel boundary portion so as to partition the spacing between the first and second substrates 1A and 2A into adjacent two closed spaces. Further, surfaces of the respective electrodes 25 and 26 are appropriately coated with a substantially insulating material (not shown) so as not to directly contact the insulating liquid 3. In the electrophoretic display apparatus described above, the first electrode 25 also functions as a reflection layer.
FIGS. 13(A) and 13(B) shows a bright display state in which the electrophoretic particles s4 are collected in an area close to the second electrode 26 to constitute a light absorbing portion enclosed by a dotted line in FIG. 13(B). In this state, for example, light 8M which enters a portion close to a pixel center portion or the light absorbing portion 13 in a direction of a normal to the substrates is first scattered isotropically by the isotropic scattering layer 12. More specifically, a part of the scattered light moves in a direction toward the first substrate 1A and is reflected by the first electrode 25 which also functions as the reflection layer and then is reflected again isotropically by the isotropic scattering layer 12. As a result, the incident light 8M is changed to reflected light 9M.
However, in such an electrophoretic display apparatus provided with the reflection layer, when light enters a portion close to the light absorbing portion 13, a part of reflected light 9M of the incident light is absorbed by the electrophoretic particles 4 present at the light absorbing portion 13 to lower a reflectance during bright state display in some cases. Further, as shown in FIG. 13(B), in the case where the second electrode 26 is formed in the neighborhood of the partition wall 7A or at the surface of the partition wall 7A, the light absorbing portion 13 and the partition wall 7A are close to each other. For this reason, a reflectance during the bright state display is lowered in some cases due to light absorption by both of the light absorbing portion 13 and the partition wall 8A.